I still have a Tower Trainer 60 size with a GMS .61 on it. Fine combination. It flies very well for a trainer including mild aerobatics. Like a few of the other guys, alas, the covering is crap. Mine now has more MonoKote on it than whatever the original crap was. However, the airplane flies well enough that it has earned a complete recover job in due time. If the forty flies as well as the sixty, go for it. I like the sixty size better because it is easier to see, it handles wind better, and sixty size planes are just easier to fly than forty size. IMHO